It was founded in 1941 by a group of Greek army officers, under the name Defenders of Northern Greece (Υπερασπισταί Βορείου Ελλάδος, YBE; Yperaspistai Voreiou Ellados, YVE), employing methods of non violent resistance.
On 28 October 1940, Italy declared war on Greece, expecting a swift victory but the invasion failed and the Italians were pushed back into Albania.
Unlike Italy and Germany, Bulgaria did not administer eastern Macedonia and the parts of Western Thrace it controlled through Greek collaborators, but annexed the area to form the province of Belomorie.
The first resistance organization in northern Greece was founded in May 1941; Eleutheria (Liberty) united people from across the political spectrum ranging from communists to Venizelists.
Barbas, E. Dortas and Captain Anastasios Sakellaridis founded Defenders of Northern Greece (YBE), a Greek nationalist resistance organization.
[2] Its membership was drawn mostly from the pre-war military and the still functioning state administration, and politically belonged to the right, professing loyalty to the Greek government in exile and King George II.
[8] YBE hoped to halt Bulgarian encroachment in Macedonia by proving their loyalty to the German authorities and in turn gaining their support.
The British also sought to foster the expansion of the right wing National Republican Greek League (EDES) in Epirus and YBE in Macedonia, to counterbalance ELAS.
[1] As part of this effort, the leadership of YBE agreed to embrace armed struggle, forming guerilla bands in rural areas.
ELAS' Macedonian units contained numerous eastern Pontic Greeks, who had migrated to Greece via the Soviet Union and become influenced by the latter in their political convictions.
In January 1944, the remnant of PAO, consisting of several hundred men, requested aid from the German authorities and they were reformed into collaborationist, counter-insurgency units.
[19][20] Its field commanders Vichos and Dangoulas signed a declaration, pledging to fight the Allies alongside Germany, while others such as Michalagas wore German army uniforms.
After the Treaty of Varkiza significantly weakened the communists, while the Greek army and gendarmerie were reformed by former members of anti-communist resistance organizations, including former collaborators.